[A procedure to obtain the recruitment using cochlear microphonic potentials]

To present an objective procedure for recruitment measure. Nowadays all recruitment methods are based on the patients' subjective responses. This procedure is based on the ratio between an increase in the cochlear microphonic potential and the increase in stimuli intensity. The system allows recruitment to be measured down to one tenth of a decibel; the precision necessary to differentiate the auditory capacity of patients.

We used a specific technique to detect cochlear microphonic potentials. We have compared the results obtained with this new technique with those determined by the Luscher method. We present 10 adults with no statistic AIM. We first tested the physical accuracy followed by measures with laboratory animals and humans.

We obtained a maximum deviation of 0.3 dB with respect to the patients' subjective appreciation. During the repetition of the objective measure with the same patients, we obtained identical results, whereas significant differences were observed with the repetitions in the subjective study.

The possibility of an objective measurement for recruitment opens up new perspectives for early diagnosis. This technique may be of assistance in the decision to place an implant or how to adapt a hearing aid. Through automatic volume control as well as the correct adjustment of the selective gain in frequency, we can also obtain the threshold audiometric profile simultaneously.